CN106947435B - High-thermal-conductivity nano carbon composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a high thermal conductivity nano-carbon composite material and a preparation method thereof. The high thermal conductivity nano-carbon composite material is mainly formed by two-step heat treatment of the aggregate of a plurality of carbon nanotubes and the graphene oxide attached to the surface of one or more carbon nanotubes in the aggregate, wherein the first step is to heat treatment. The heat treatment is carried out in a reducing atmosphere, and the heat treatment temperature is 200-500 °C, and the second-step heat treatment is carried out in a protective atmosphere, and the heat treatment temperature is 1500-3000 °C. Compared with the existing carbon nanotube/graphene composite material, the high thermal conductivity nano carbon composite material provided by the present invention has significantly improved thermal conductivity and other properties, and also has high flexibility, high electrical conductivity, excellent mechanical properties, etc. Moreover, the preparation process is simple and controllable, the energy consumption is low, and the large-scale implementation is easy.

Description

High thermal conductivity nano-carbon composite material and preparation method thereof

technical field

The invention relates to a nano-carbon composite material and a preparation method thereof, in particular to a high-thermal-conductivity nano-carbon composite material, such as a high-thermal-conductivity flexible carbon nanotube/graphene composite film and a preparation method thereof, belonging to the field of material science.

Background technique

With the rapid development of high-power micro-nano electronic devices, semiconductor laser displays, multi-core smart phones and mobile devices, the heat generated by the electronic components of the equipment needs to be evacuated in time to ensure that they can work efficiently and reliably. The primary influencing factor of device lifetime. At present, metal materials (copper, aluminum) and graphite film heat dissipation materials are widely used in the market. The former has low thermal conductivity (copper: aluminum), the latter has poor flexibility and is not resistant to bending, while nano-carbon materials have high thermal conductivity and high temperature resistance. , high mechanical flexibility, easy to modulate the interface thermal resistance and other characteristics, it is an ideal material for a new generation of high heat dissipation.

Typical carbon nanomaterials mainly include carbon nanotubes and graphene, which have unique one-dimensional and two-dimensional layered lattice structures, respectively, and these special structures also endow them with high thermal conductivity and electron mobility, good chemical stability, It has the advantages of low mass density and strong mechanical properties. At the same time, carbon nanotubes are relatively large in length and diameter and have good flexibility, and graphene has a large lamellar structure. At present, researchers have tried to combine the two, in order to obtain carbon nanomaterials with both advantages.

For example, CN104029461A discloses a preparation method of graphene/carbon nanotube/graphite film composite material, which firstly carbonizes and graphitizes the polymer film material, and then adopts chemical vapor deposition method to mix graphene and carbon nanotubes The particles are deposited on the surface of the graphite film, and then the graphene/carbon nanotube/graphite film is compositely formed by a rewinder.

For another example, CN103626172A discloses a method for preparing graphite paper with high thermal conductivity, which uses a magnetron sputtering system to prepare a nickel layer of 10-500 nm on a graphite sheet with a thickness of 0.2-1 mm and annealing at high temperature, and then uses chemical vapor deposition method to prepare a nickel layer of 10-500 nm on a graphite sheet with a thickness of 0.2-1 mm. Graphene and carbon nanotubes are grown on the surface of the graphite sheet coated with nickel layer, and then high thermal conductivity graphite paper is obtained by high pressure treatment.

However, in the graphene/carbon nanotube composite materials obtained in the prior art, graphene and carbon nanotubes are basically simple physical combinations, and fail to form a better synergistic effect, so the thermal conductivity of the composite materials is also compared. Graphene or carbon nanotubes have less lift. On the other hand, the preparation process of the existing graphene/carbon nanotube composite materials is complicated, the energy consumption is high, and the controllability is poor.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a high thermal conductivity nano-carbon composite material and a preparation method thereof to overcome the deficiencies in the prior art.

To achieve the above object, the present invention provides the following technical solutions:

The embodiment of the present invention provides a high thermal conductivity nano-carbon composite material, which comprises:

Aggregates formed by the aggregation of multiple carbon nanotubes,

Graphene, bound to the surface of one or more carbon nanotubes in the aggregate;

Wherein, at the junction of the graphene and the carbon nanotube, some carbon atoms on the carbon nanotube are connected with some carbon atoms on the graphene to form sp3 valence bonds.

Further, the thermal conductivity of the high thermal conductivity carbon nanocomposite material is above 600W/m, preferably above 1200W/m, particularly preferably 1200W/m～2200W/m; and/or, the high thermal conductivity nanocarbon composite material The electrical conductivity is above 4×10 ⁴ S/m, preferably above 3×10 ⁵ S/m, especially preferably 3×10 ⁵ S/m～1×10 ⁶ S/m; and/or, the high The tensile strength of the thermally conductive nano-carbon composite material is above 300 MPa, preferably above 2000 MPa, particularly preferably 2000-2600 Mpa, and the Young's modulus is above 40 GPa, preferably 40-220 GPa.

The embodiment of the present invention provides a nano-carbon composite material with high thermal conductivity, which is mainly composed of an aggregate of multiple carbon nanotubes and graphene oxide attached to the surface of one or more carbon nanotubes in the aggregate. Step heat treatment is formed, wherein the first heat treatment is carried out in a reducing atmosphere, and the heat treatment temperature is 200 to 500 ° C, preferably 300 to 350 ° C; the second heat treatment is carried out in a protective atmosphere, and the heat treatment temperature is 1500 ~ 3000 ° C °C, preferably 2000 to 3000 °C.

The embodiment of the present invention provides a preparation method of a high thermal conductivity nano-carbon composite material, comprising:

provide aggregates formed by agglomeration of a plurality of carbon nanotubes,

providing a graphene oxide dispersion, and incorporating the graphene oxide dispersion into the aggregate to form a carbon nanotube/graphene composite precursor;

The carbon nanotube/graphene composite precursor is placed in a reducing atmosphere and heat treated at 200-500°C (preferably 300-350°C) for more than 15min, then transferred to a protective atmosphere and heated at 1500-3000°C ( Preferably, the heat treatment is performed at 2000 to 3000° C. for 15 min or more.

The embodiment of the present invention provides a high thermal conductivity flexible nano-carbon composite film, which comprises:

The carbon nanotube continuum is composed of a plurality of carbon nanotubes;

at least the graphene attached to the surface of the carbon nanotube continuum;

Wherein, at the junction of the graphene and one or more carbon nanotubes in the carbon nanotube continuum, some carbon atoms on the carbon nanotubes are connected with some carbon atoms on the graphene to form sp3 valence bonds.

The embodiment of the present invention provides a preparation method of a high thermal conductivity flexible nano-carbon composite film, which includes:

(1) provide graphene oxide solution;

(2) the graphene oxide solution is continuously and uniformly integrated into the surface of the carbon nanotube continuum to form a carbon nanotube/graphene composite film precursor;

(3) placing the carbon nanotube/graphene composite film precursor in a reducing atmosphere, treating at 200-500° C. (preferably 300-350° C.) for 15-120 min, and then cooling to room temperature;

(4) placing the carbon nanotube/graphene composite film obtained in step (3) in a protective atmosphere, and treating at 1500-3000° C. (preferably 2,000-3000° C.) for 15-360 minutes to obtain the high thermal conductivity and flexibility Nanocarbon composite film.

Compared with the prior art, the thermal conductivity and other properties of the high thermal conductivity nano-carbon composite material provided by the present invention are significantly improved, and at the same time, it also has the characteristics of high flexibility, high electrical conductivity and excellent mechanical properties, and the preparation process is simple and can be used. Control, low energy consumption, easy to scale implementation.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

1 is a Raman spectrum diagram of a carbon nanotube/graphene composite film before and after the first step of heat treatment and the second step of heat treatment in a typical embodiment of the present invention.

FIG. 2 is a SEM photograph of a carbon nanotube/graphene composite film finally obtained in a typical embodiment of the present invention.

Detailed ways

An embodiment of one aspect of the present invention provides a high thermal conductivity nano-carbon composite material, comprising:

Aggregates formed by the aggregation of multiple carbon nanotubes,

Graphene, bound to the surface of one or more carbon nanotubes in the aggregate;

Wherein, at the junction of the graphene and the carbon nanotube, some carbon atoms on the carbon nanotube are connected with some carbon atoms on the graphene to form sp3 valence bonds.

In some embodiments, at least one graphene sheet overlaps between at least two carbon nanotubes. That is, at least one graphene sheet simultaneously covers the surfaces of two or more carbon nanotubes. In this way, the thermal conductivity and electrical conductivity of the formed high thermal conductivity nano-carbon composite material in all directions can be more effectively improved.

Further, the thermal conductivity of the high thermal conductivity nano-carbon composite material is above 600W/m, preferably above 1200W/m, particularly preferably 1200W/m˜2200W/m.

Further, the electrical conductivity of the high thermal conductivity nano-carbon composite material is above 4×10 ⁴ S/m, preferably above 3×10 ⁵ S/m, especially preferably 3×10 ⁵ S/m～1×10 ⁶ S/m.

Further, the tensile strength of the high thermal conductivity nano-carbon composite material is above 300MPa, preferably above 2000MPa, especially preferably 2000-2600Mpa, and the Young's modulus is above 40GPa, preferably 40-220GPa.

An embodiment of one aspect of the present invention provides a high thermal conductivity nano-carbon composite material, which is mainly composed of agglomerates of a plurality of carbon nanotubes and oxidation of the surface of one or more carbon nanotubes attached to the agglomerates Graphene is formed by two-step heat treatment, wherein the first heat treatment is carried out in a reducing atmosphere, the heat treatment temperature is 200-500 ° C, preferably 300-350 ° C, the second heat treatment is carried out in a protective atmosphere, and the heat treatment temperature is It is 1500-3000 degreeC, Preferably it is 2000-3000 degreeC.

In some specific embodiments, the pressure conditions used in the second heat treatment process are 20-40 MPa.

Further, the gas used to form the reducing atmosphere includes any one or a combination of two or more of air, hydrogen, carbon monoxide, hydrogen sulfide, and methane, but is not limited thereto.

Further, the gas used to form the protective atmosphere includes any one or a combination of two or more of inert gas and nitrogen, but is not limited thereto.

An embodiment of one aspect of the present invention provides a method for preparing a high thermal conductivity nano-carbon composite material, comprising:

provide aggregates formed by agglomeration of a plurality of carbon nanotubes,

providing a graphene oxide dispersion, and incorporating the graphene oxide dispersion into the aggregate to form a carbon nanotube/graphene composite precursor;

The carbon nanotube/graphene composite precursor is placed in a reducing atmosphere and heat-treated at 200-500 ° C (preferably 300-350 ° C) for more than 15 min (preferably more than 30 min), and then transferred to a protective atmosphere and Heat treatment at 1500-3000°C (preferably 2000-3000°C) for 15 min or more.

More preferably, the concentration of the graphene oxide solution is 0.1-3 mg/ml.

More preferably, the radial dimension of the graphene oxide is 10 nm-1 mm, and the thickness is 0.24 nm-2 nm.

Further, the graphene oxide includes any one or a combination of two or more of single-layer, double-layer, and multi-layer graphene oxide.

Particularly preferably, the radial dimension of the graphene oxide is >0.15 μm, and the number of lamellae is 2-5.

An embodiment of one aspect of the present invention provides a highly thermally conductive flexible nano-carbon composite film, comprising:

The carbon nanotube continuum is composed of a plurality of carbon nanotubes;

at least the graphene attached to the surface of the carbon nanotube continuum;

Wherein, at the junction of the graphene and one or more carbon nanotubes in the carbon nanotube continuum, some carbon atoms on the carbon nanotubes are connected with some carbon atoms on the graphene to form sp3 valence bonds.

Further, the thermal conductivity of the high thermal conductivity flexible nano-carbon composite film is above 600W/m, preferably above 1200W/m, especially preferably 1200W/m～2200W/m, and the tensile strength is above 300MPa, preferably above 2000MPa , especially preferably 2000-2600Mpa, and the Young's modulus is above 40GPa, preferably 40-220GPa.

Further, the electrical conductivity of the high thermal conductivity flexible nano-carbon composite film is above 4×10 ⁴ S/m, preferably above 3×10 ⁵ S/m, especially preferably 3×10 ⁵ S/m～1×10 ⁶ S/m

More preferably, the thickness of the high thermal conductivity flexible nano-carbon composite film is 0.5 μm˜2 mm.

Further, the carbon nanotube continuum includes a carbon nanotube film made by any one of the floating catalysis method, the array growth film pulling method, and the direct suction filtration method, and of course other forms of carbon nanotube continuum can also be used. body, but preferably a continuum formed by dense aggregation of carbon nanotubes, such as a continuum containing a pore structure.

Wherein, the carbon nanotubes can be selected from any one or a combination of single-wall, few-wall, and multi-wall carbon nanotubes.

Wherein, the material selection range of the carbon nanotube continuum and graphene can be as described above, and the gas used to form the reducing atmosphere and the protective atmosphere can also be as described above, which will not be repeated here.

An embodiment of one aspect of the present invention provides a method for preparing the high thermal conductivity flexible nano-carbon composite film, comprising:

(1) provide graphene oxide solution;

(2) the graphene oxide solution is continuously and uniformly integrated into the surface of the carbon nanotube continuum to form a carbon nanotube/graphene composite film precursor;

(3) placing the carbon nanotube/graphene composite film precursor in a reducing atmosphere, treating at 300-350° C. for 30-120 min, and then dropping to room temperature;

(4) placing the carbon nanotube/graphene composite film obtained in step (3) in a protective atmosphere, and treating at 2000-3000° C. for 15-360 min to obtain the high thermal conductivity flexible nano-carbon composite film.

In some embodiments, in step (2), the graphene oxide solution is continuously and uniformly integrated into the surface of the carbon nanotube continuum while the carbon nanotube continuum is continuously traveling along a set direction. .

In some specific embodiments, step (2) may include: using a winding method to wind the carbon nanotube continuum on a winding body (for example, a diameter of 10cm-1000cm) cylinder), the winding speed is 0.5-10 m/min (for example, it may be preferably 0.5-5 m/min), and at the same time, the graphene oxide solution is continuously and uniformly sprayed on the surface of the carbon nanotube continuum to obtain the obtained The carbon nanotube/graphene composite film precursor.

Further, in step (2), while the winding body is rotated, the winding body can also be moved along its axial direction.

For example, the steps included in a method for preparing a highly thermally conductive flexible nano-carbon composite film of the present invention are as follows:

(1) dissolving graphene oxide in a polar solvent, and ultrasonically treating to obtain a graphene oxide solution of a certain concentration after stirring;

(2) using the winding method to wind the carbon nanotube continuum on a cylinder that can be rolled radially and moved axially, and at the same time, the graphene oxide solution is continuously integrated into the surface of the carbon nanotube continuum to obtain carbon nanotube/ Graphene composite film precursor;

(3) annealing the obtained carbon nanotube/graphene composite film precursor in a reducing atmosphere to remove impurities and oxygen-containing functional groups on the surface of carbon nanotubes to obtain a carbon nanotube and graphene composite nano-carbon film material;

(4) ultra-high temperature annealing of the carbon nano-film material in a high-temperature inert atmosphere to remove impurities on the surface of carbon nanotubes and graphene, and simultaneously improve the crystallinity of carbon nanotubes and graphene.

In some embodiments, step (2) may further include: removing the solvent in the carbon nanotube/graphene composite film precursor by hot pressing.

Wherein, the material selection range of the carbon nanotube continuum and graphene can be as described above, and the gas used to form the reducing atmosphere and the protective atmosphere can also be as described above, which will not be repeated here.

In some preferred embodiments, step (1) includes: dispersing graphene oxide with a radial size > 0.15 μm and a number of lamellae from 2 to 5 in a polar solvent to form a graphene oxide suspension, and then ultrasonicating treatment, the ultrasonic power is 20-60w, the treatment time is 5-30min, and a graphene oxide solution with a concentration of 0.1-3mg/ml is obtained.

Further, the polar solvent may preferably be selected from any one or a combination of two or more of water, methanol, ethanol, and acetone, but is not limited thereto.

The present invention reduces graphene oxide to graphene by using one-dimensional carbon nanotubes and two-dimensional graphene as raw materials through reduction treatment (ie, the aforementioned first-step heat treatment), and removes carbon nanotubes and graphene. Impurities (such as amorphous carbon), and then through the aforementioned second-step heat treatment to generate sp3 covalent bonds between carbon nanotubes and graphene, and at the same time, the defects on carbon nanotubes and graphene are repaired, so that carbon nanotubes and graphene are repaired. The crystallinity of nanotubes and graphene is synergistically improved, and finally a carbon nanotube/graphene composite material with high thermal conductivity is obtained, and its thermal conductivity is far superior to that of carbon nanotubes, graphene or existing carbon nanotubes/graphite At the same time, it also has the characteristics of high conductivity, high flexibility and excellent mechanical properties, and its preparation process is simple, high controllability, low energy consumption, which is conducive to large-scale production.

The technical solutions of the present invention will be further explained below with reference to several embodiments.

Example 1:

Using carbon nanotube continuous film (prepared by floating catalysis method), graphene oxide (average radial size is more than 0.15 μm, the number of sheets is about 2 to 5) as raw material, through the preparation of carbon nanotube/graphene composite film precursor , the reduction process of the carbon nanotube/graphene composite film (the first heat treatment) and the second heat treatment process of the carbon nanotube/graphene composite film to meet the requirements of high thermal conductivity, high flexibility and high mechanical properties, The process is as follows:

A. Preparation of carbon nanotube/graphene composite film precursors

Dissolve 5mg of graphene oxide powder in 10ml of deionized water and ethanol mixture, the volume ratio of deionized water to ethanol is about 1:1, and after magnetic stirring to obtain graphene oxide suspension, ultrasonic treatment, ultrasonic power 30w, ultrasonic Time 5min to obtain graphene oxide solution with a concentration of about 0.5mg/ml.

The continuous film of carbon nanotubes was wound on a cylinder with a diameter of 3 cm by a winding method, the winding speed was about 2 m/min, and the winding time was 10 minutes. At the same time, the graphene oxide solution was uniformly sprayed at a flow rate of about 1 ml/min. To the surface of the carbon nanotube continuous film, a carbon nanotube/graphene film is formed, and then the water and solvent molecules in the film are removed by hot pressing. The temperature is about 90 ° C, the pressure is about 10 MPa, and the hot pressing time is 30 minutes. The Raman spectrum of the carbon nanotube/graphene composite film precursor is shown in Figure 1.

B. Reduction process of carbon nanotube/graphene composite film

The carbon nanotube/graphene composite film precursor is placed in a high-temperature furnace, and an air atmosphere is introduced, and the temperature is raised to 350 ° C from normal temperature, and the heating rate is 5 ° C/min, and the temperature is lowered to room temperature after being kept for 30 minutes. The main purpose is to : (1) reducing graphene oxide to graphene by using oxygen atmosphere in the air; (2) removing amorphous carbon and small molecular volatile substances in carbon nanotubes. The Raman spectrum of the carbon nanotube/graphene composite film treated by this step is shown in Figure 1.

C. The second heat treatment process of carbon nanotube/graphene composite film

The carbon nanotube/graphene composite film obtained in step B was placed in a high-temperature furnace, filled with nitrogen atmosphere to a pressure of about 40Mpa, and heated to 2800 ° C from normal temperature, and kept for 25min. A sp3 valence bond is generated between the carbon nanotubes (see Figure 1), and the defects of the carbon nanotubes themselves are partially healed to form a six-membered ring with a complete structure, and the crystallinity of the carbon nanotubes is effectively improved.

The morphology of the carbon nanotube/graphene composite film processed by the above steps can be seen in Figure 2. Its thickness is about 5 μm, the density is about 1.1 g/cm ³ , the tensile strength is about 2.6 GPa, the Young’s modulus is about 220 GPa, and the thermal conductivity is about 220 GPa. About 2120W/mK, the conductivity is about 4×10 ⁵ S/m.

Example 2:

Using carbon nanotube continuous thin film (prepared by array growth film method), graphene oxide (same as Example 1) as raw material, through the preparation of carbon nanotube/graphene composite film precursor, carbon nanotube/graphene composite film The reduction process (the first step of heat treatment) and the second step of heat treatment of the carbon nanotube/graphene composite film are used to achieve the requirements of high thermal conductivity, high flexibility and high mechanical properties. The process is as follows:

A. Preparation of carbon nanotube/graphene composite film precursors

Dissolve 10mg of graphene oxide powder in 10ml of deionized water and ethanol mixture, the volume ratio of deionized water and ethanol is about 1:1, and then ultrasonically treat the graphene oxide suspension after magnetic stirring, ultrasonic power 30w, ultrasonic Time 10min to obtain graphene oxide solution with a concentration of about 1mg/ml.

The continuous film of carbon nanotubes was wound on a cylinder with a diameter of about 10cm by the winding method, the winding speed was 5m/min, and the winding time was 10min. At the same time, the graphene oxide solution was evenly sprayed at a flow rate of 2ml/min The surface of the carbon nanotube continuous film is formed into a carbon nanotube/graphene film, and then the water and solvent molecules in the film are removed by hot pressing treatment. The temperature is 90 °C, the pressure is 10 MPa, and the hot pressing time is 30 minutes to obtain carbon nanotubes with a thickness of about 8 μm. / Graphene composite film precursor.

B. Reduction process of carbon nanotube/graphene composite film

The carbon nanotube/graphene composite film precursor is placed in a high-temperature furnace, and a hydrogen sulfide atmosphere is introduced, and the temperature is raised from normal temperature to 200 ° C, the heating rate is 5 ° C/min, and the temperature is lowered to room temperature after being kept for 30 minutes. The main purpose It consists of: (1) reducing graphene oxide to graphene by using hydrogen sulfide atmosphere; (2) removing amorphous carbon and small molecular volatile substances in carbon nanotubes.

C. The second heat treatment process of carbon nanotube/graphene composite film

The carbon nanotube/graphene composite film obtained in step B was placed in a high-temperature furnace, filled with nitrogen atmosphere to a pressure of about 20Mpa, and heated to 3000 ° C from normal temperature, and kept for 15min. Sp3 bonds are generated between the carbon nanotubes, and the defects of the carbon nanotubes themselves are partially healed to form a six-membered ring with a complete structure, and the crystallinity of the carbon nanotubes is effectively improved.

The thickness of the carbon nanotube/graphene composite film processed through the above steps is about 8 μm, the density is about 1.18 g/cm ³ , the tensile strength is about 2.0 GPa, the Young’s modulus is about 130 GPa, the thermal conductivity is about 1920 W/mK, and the electrical conductivity is about 6×10 ⁵ S/m.

Example 3:

Using carbon nanotube continuous film (prepared by suction filtration), graphene oxide (same as Example 1) as raw material, through the preparation of carbon nanotube/graphene composite film precursor, the reduction of carbon nanotube/graphene composite film Process (the first heat treatment) and the second heat treatment process of the carbon nanotube/graphene composite film to achieve the requirements of high thermal conductivity, high flexibility and high mechanical properties, and the process is as follows:

A. Preparation of carbon nanotube/graphene composite film precursors

Dissolve 30mg of graphene oxide powder in 10ml of deionized water and acetone mixture, the volume ratio of deionized water to ethanol is 2:1, and after magnetic stirring to obtain graphene oxide suspension, ultrasonic treatment, ultrasonic power 60w, ultrasonic Time 20min to obtain graphene oxide solution with a concentration of 3mg/ml.

The continuous film of carbon nanotubes was wound on a cylinder with a diameter of about 20 cm by the winding method, the winding speed was 10 m/min, and the winding time was 10 min. At the same time, the graphene oxide solution was evenly sprayed on the The surface of the carbon nanotube continuous film is formed into a carbon nanotube/graphene film, and then the water and solvent molecules in the film are removed by hot pressing. / Graphene composite film precursor.

B. Reduction process of carbon nanotube/graphene composite film

The carbon nanotube/graphene composite film with a thickness of 22 μm was placed in a high-temperature furnace, and a methane atmosphere was introduced, and the temperature was increased from normal temperature to 300 ° C, the heating rate was 5 ° C/min, and the temperature was kept for 30 minutes. (1) reducing graphene oxide to graphene using methane atmosphere; (2) removing amorphous carbon and small molecular volatile substances in carbon nanotubes;

C. The second heat treatment process of carbon nanotube/graphene composite film

The carbon nanotube/graphene composite film obtained in step B is placed in a high-temperature furnace, filled with argon gas to a pressure of about 10Mpa, and heated to 1500 ° C from normal temperature, and maintained for 360min. Sp3 bonds are generated between the carbon nanotubes, and the defects of the carbon nanotubes themselves are partially healed to form a six-membered ring with a complete structure, and the crystallinity of the carbon nanotubes is effectively improved.

The carbon nanotube/graphene composite film processed through the above steps has a thickness of about 22 μm, a density of about 1.25 g/cm ³ , a tensile strength of about 1.8 GPa, a Young’s modulus of about 120 GPa, a thermal conductivity of about 1850 W/mK, and an electrical conductivity of about 1.8 GPa. 1×10 ⁶ S/m.

Example 4:

Using carbon nanotube continuous thin film (prepared by array growth film method), graphene oxide (same as Example 1) as raw material, through the preparation of carbon nanotube/graphene composite film precursor, carbon nanotube/graphene composite film The reduction process (the first step of heat treatment) and the second step of heat treatment of the carbon nanotube/graphene composite film are used to achieve the requirements of high thermal conductivity, high flexibility and high mechanical properties. The process is as follows:

A. Preparation of carbon nanotube/graphene composite film precursors

Dissolve 10mg of graphene oxide powder in 10ml of deionized water and ethanol mixture, the volume ratio of deionized water and ethanol is about 1:1, and then ultrasonically treat the graphene oxide suspension after magnetic stirring, ultrasonic power 30w, ultrasonic Time 10min to obtain graphene oxide solution with a concentration of about 5mg/ml.

The carbon nanotube continuous film was wound on a cylinder with a diameter of 3 cm by the winding method, the winding speed was 1 m/min, and the winding time was 10 minutes. On the surface of the continuous film of nanotubes, a carbon nanotube/graphene film is formed, and then the water and solvent molecules in the film are removed by hot pressing treatment, the temperature is 90 ° C, the pressure is 10 MPa, and the hot pressing time is 30 minutes, to obtain carbon nanotubes with a thickness of about 8 μm/ Graphene composite film precursor.

B. Reduction process of carbon nanotube/graphene composite film

The carbon nanotube/graphene composite film precursor is placed in a high-temperature furnace, and a carbon monoxide atmosphere is introduced, and the temperature is raised to 500 ° C from normal temperature, the heating rate is 5 ° C/min, and the temperature is lowered to room temperature after being kept for 15 minutes. The main purpose is to : (1) reducing graphene oxide to graphene by using carbon monoxide atmosphere; (2) removing amorphous carbon and small molecular volatile substances in carbon nanotubes.

C. The second heat treatment process of carbon nanotube/graphene composite film

The carbon nanotube/graphene composite film obtained in step B is placed in a high-temperature furnace, filled with argon gas to a pressure of about 4Mpa, and heated to 2000 ° C from normal temperature, and kept for 60 minutes. Sp3 bonds are generated between the carbon nanotubes, and the defects of the carbon nanotubes themselves are partially healed to form a six-membered ring with a complete structure, and the crystallinity of the carbon nanotubes is effectively improved.

The carbon nanotube/graphene composite film processed through the above steps has a thickness of about 0.5 μm, a density of about 1.18 g/cm ³ , a tensile strength of about 2.0 GPa, a Young’s modulus of about 150 GPa, a thermal conductivity of about 2200 W/mK, and an electrical conductivity of about 2.0 GPa. About 5×10 ⁵ S/m.

Finally, it should also be noted that the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device comprising a series of elements includes not only those elements, but also Also included are other elements not expressly listed or inherent to such a process, method, article or apparatus.

Claims (25)

1. A highly thermally conductive nanocarbon composite material, characterized by comprising:

an aggregate formed by aggregating a plurality of carbon nanotubes,

graphene bound to the surface of one or more carbon nanotubes in the aggregate, wherein at least one graphene sheet is lapped between at least two carbon nanotubes;

and at the joint of the graphene and the carbon nanotube, part of carbon atoms on the carbon nanotube are connected with part of carbon atoms on the graphene to form sp3 valence bonds.

2. The nanocarbon composite material with high thermal conductivity as claimed in claim 1, wherein the nanocarbon composite material with high thermal conductivity has a thermal conductivity of 600W/m or more and an electrical conductivity of 4 × 10⁴S/m or more, tensile strength of 300MPa or more, and Young' S modulus of 40GPa or more.

3. The nanocarbon composite material of claim 2, wherein the nanocarbon composite material has a thermal conductivity of 1200W/m or more and an electrical conductivity of 3 × 10⁵S/m is more than or equal to 2000MPa in tensile strength.

4. The high thermal conductivity nanocarbon composite material according to claim 3, wherein the thermal conductivity of the high thermal conductivity nanocarbon composite material is 1200W/m to 2200W/m, and the electrical conductivity is 3 × 10⁵S/m～1×10⁶S/m, tensile strength of 2000-2600 Mpa, and Young' S modulus of 40-220 GPa.

5. A high-thermal-conductivity nano carbon composite material is characterized by mainly comprising an aggregate of a plurality of carbon nanotubes and graphene oxide attached to the surface of one or more carbon nanotubes in the aggregate through two-step heat treatment, wherein the first-step heat treatment is carried out in a reducing atmosphere, the heat treatment temperature is 200-500 ℃, and gas for forming the reducing atmosphere comprises any one or the combination of more than two of air, hydrogen, carbon monoxide, hydrogen sulfide and methane; and the second step of heat treatment is carried out in a protective atmosphere, the adopted pressure condition is 4-40 MPa, the heat treatment temperature is 1500-3000 ℃, and the gas for forming the protective atmosphere comprises any one or the combination of more than two of inert gas and nitrogen.

6. The highly thermally conductive nanocarbon composite material according to claim 5, wherein: in the first step of heat treatment, the adopted heat treatment temperature is 300-350 ℃; in the second step of heat treatment, the adopted heat treatment temperature is 2000-3000 ℃.

7. The method for preparing the highly thermally conductive nanocarbon composite material according to any one of claims 1 to 5, comprising:

providing an aggregate formed by aggregation of a plurality of carbon nanotubes,

providing a graphene oxide dispersion liquid, and blending the graphene oxide dispersion liquid into the aggregate to form a carbon nanotube/graphene composite precursor, wherein the graphene oxide comprises any one or a combination of more than two of single-layer graphene oxide and multi-layer graphene oxide;

placing the carbon nano tube/graphene composite precursor in a reducing atmosphere, carrying out heat treatment at 200-500 ℃ for more than 15min, then transferring the precursor into a protective atmosphere, and carrying out heat treatment at 1500-3000 ℃ for more than 15 min;

the gas for forming the reducing atmosphere comprises any one or combination of more than two of air, hydrogen, carbon monoxide, hydrogen sulfide and methane, and the gas for forming the protective atmosphere comprises any one or combination of more than two of inert gas and nitrogen.

8. The method of claim 7, wherein: the concentration of the graphene oxide solution is 0.1-10 mg/ml.

9. The method of claim 8, wherein: the concentration of the graphene oxide solution is 0.1-3 mg/ml.

10. The method of claim 7, wherein: the radial size of the graphene oxide is 10 nm-1 mm, and the thickness of the graphene oxide is 0.24 nm-2 nm.

11. A high thermal conductivity flexible nanocarbon composite film, characterized by comprising:

a carbon nanotube continuum comprised of a plurality of carbon nanotubes;

graphene attached to at least the surface of the carbon nanotube continuum, wherein the graphene comprises any one of single-layer graphene and multi-layer graphene or a combination of two or more of the single-layer graphene and the multi-layer graphene;

wherein, at the joint of the graphene and one or more carbon nanotubes in the carbon nanotube continuum, part of carbon atoms on the carbon nanotubes are connected with part of carbon atoms on the graphene to form sp3 valence bonds;

the high-thermal-conductivity flexible nano carbon composite film has the thermal conductivity coefficient of more than 600W/m, the tensile strength of more than 300MPa, the Young modulus of more than 40GPa, and the electrical conductivity of 4 × 10⁴And S/m is more than or equal to.

12. The high thermal conductivity flexible nanocarbon composite film according to claim 11, wherein the high thermal conductivity flexible nanocarbon composite film has a thermal conductivity of 1200W/m or more, a tensile strength of 2000MPa or more, and an electrical conductivity of 3 × 10⁵And S/m is more than or equal to.

13. The high thermal conductivity flexible nanocarbon composite film according to claim 12, wherein: the heat conductivity coefficient of the high-heat-conductivity flexible nano carbon composite film is 1200W/m ℃, (E) c2200W/m, tensile strength of 2000-2600 Mpa, Young modulus of 40-220 GPa, electric conductivity of 3 × 10⁵S/m～1×10⁶S/m。

14. The high thermal conductivity flexible nanocarbon composite film according to claim 11, wherein: the thickness of the high-heat-conductivity flexible nano carbon composite membrane is 0.5 mu m-2 mm.

15. The high thermal conductivity flexible nanocarbon composite film according to claim 11, wherein: the carbon nano tube continuum is a carbon nano tube film prepared by any one of a floating catalysis method, an array growth film drawing method and a direct suction filtration method.

16. The high thermal conductivity flexible nanocarbon composite film according to claim 11, wherein: the radial size of the graphene is 10 nm-1 mm, and the thickness of the graphene is 0.24 nm-2 nm.

17. A method for preparing the high thermal conductive flexible nanocarbon composite film according to any one of claims 11 to 16, comprising:

(1) providing a graphene oxide solution, wherein the graphene oxide comprises any one of single-layer graphene oxide and multi-layer graphene oxide or a combination of more than two of the single-layer graphene oxide and the multi-layer graphene oxide;

(2) continuously and uniformly melting the graphene oxide solution on the surface of the carbon nanotube continuous body to form a carbon nanotube/graphene composite membrane precursor;

(3) placing the carbon nanotube/graphene composite membrane precursor in a reducing atmosphere, treating at 200-500 ℃ for 15-120 min, and cooling to room temperature, wherein the gas for forming the reducing atmosphere comprises any one or a combination of more than two of air, hydrogen, carbon monoxide, hydrogen sulfide and methane;

(4) and (3) placing the carbon nanotube/graphene composite membrane obtained in the step (3) in a protective atmosphere, and treating at 1500-3000 ℃ for 15-360 min to obtain the high-thermal-conductivity flexible nano carbon composite membrane, wherein the gas for forming the protective atmosphere comprises any one or a combination of more than two of inert gases and nitrogen.

18. The method of claim 17, wherein: in the step (2), the graphene oxide solution is continuously and uniformly melted on the surface of the carbon nanotube continuum while the carbon nanotube continuum is continuously advanced in a set direction.

19. The method of claim 17, wherein step (2) comprises: and winding the carbon nanotube continuum on a winding body by adopting a winding method, wherein the diameter of the winding body is 1-1000 cm, the winding speed is 0.5-10 m/min, and simultaneously, continuously and uniformly spraying the graphene oxide solution on the surface of the carbon nanotube continuum to obtain the carbon nanotube/graphene composite membrane precursor.

20. The method of claim 19, wherein: the diameter of the winding body is 3-20 cm, and the winding speed is 5-10 m/min.

21. The method of claim 17, wherein step (2) further comprises: and removing the solvent in the precursor of the carbon nano tube/graphene composite membrane by adopting a hot pressing mode.

22. The method of claim 17, wherein: the carbon nano tube continuum is a carbon nano tube film prepared by any one of a floating catalysis method, an array growth film drawing method and a direct suction filtration method.

23. The method of claim 17, wherein: the radial size of the graphene is 10 nm-1 mm, and the thickness of the graphene is 0.24 nm-2 nm.

24. The method of claim 17, wherein step (1) comprises: graphene oxide with the radial size of more than 0.15 mu m and the number of sheets of 2-5 is dispersed in a polar solvent to form a graphene oxide suspension, and then ultrasonic treatment is carried out, wherein the ultrasonic power is 20-60 w, the treatment time is 5-30 min, and a graphene oxide solution with the concentration of 0.1-3 mg/ml is obtained.

25. The method of claim 24, wherein: the polar solvent is selected from one or the combination of more than two of water, methanol, ethanol and acetone.

Images